1. Field of the Invention
The present invention relates generally to transient signal detection, and in particular, to a High-Speed Transient Recorder and Power Quality Analyzer in a Revenue Grade Power Meter. The purpose of the unit is to record high-speed power quality events such as spikes and transients with a scan rate of 5 KHz to 20 MHz or higher. This allows a monitor, such as a power company, to examine the high-speed events affecting the quality of the power being provided by the power company to an end user (e.g., a utility""s customer).
2. Background of the Invention
Conventionally, high-speed power quality events such as spikes and transients were ascertained by a piece of equipment separate from the power meter. This piece of portable equipment is high in cost and is usually brought to the site to monitor power quality after the customer has complained about power quality problems. Then, in order to detect the spikes and transients, this piece of portable monitoring equipment must be used until the power problem occurs yet another time. As a result, correcting any problems that may lead to these high-speed power quality events may take a very long time.
FIG. 1 is a graphical illustration of metered power consumed by a user or provided by a provider at a scanning rate known in the art for the purposes of revenue calculation, e.g. any rate greater than 120 Hz, but usually between 2 KHz and 10 KHz, as performed by a conventional power meter. The graph of the sinusoidal wave is determined by taking a power sample at every tn, determined according to the sampling rate. The common scanning rate that provides a power sample at every tn, while suitable for metering power consumption by a user for the purposes of revenue calculations, is not capable of determining when high-speed power quality events occur. High-speed power quality events such as transients and spikes occur at a rate much faster than the common scanning rate used for power metering. Therefore, unless the high-speed power quality event happens to occur at the exact time the sample is being taken (tn), it will go undetected. This concept will be explained further with reference to FIG. 1 and FIGS. 2A-2D.
As stated above, FIG. 1 is a graph illustrating power metering for the purposes of revenue calculations at a rate where a sample is taken at every interval tn. However, no samples are being taken in the time intervals labeled A, B, C, and D, as these time periods fall between the samples taken at tn. FIGS. 2A-2D are graphical representations of the high-speed power quality events that might occur at times A, B, C, and D, respectively, and that go undetected due to the power meter""s slow sampling rate.
Therefore, a need exists for a revenue grade power meter that performs the conventional task of monitoring power and also has the ability to capture high-speed power quality events when they first occur in order to more efficiently monitor and control power usage and efficiency.
It is, therefore, an object of the present invention to provide a system incorporating high-speed electrical monitoring along with revenue metering functions in an electric meter provided to a customer used for billing.
It is another object of the present invention to provide a system for measuring and recording high-speed electrical events monitored in the meter provided to the customer.
It is yet another object of the present invention to record waveforms of the high-speed electrical events monitored in the meter provided to the customer.
In order to achieve the above and other objects, a preferred embodiment of a revenue grade power meter capable of detecting high-speed power quality events is provided. Other than comprising components found in a conventional revenue grade power meter, the power meter further comprises a plurality of digital high-speed peak detectors for detecting high-speed quality events of the power consumed by the user at a high-speed scanning rate, the high-speed scanning rate being faster than a conventional scanning rate used in a conventional power meter; a wave analysis component for comparing the detected high-speed quality events to a predetermined threshold, storing the detected high-speed quality events in time synchronization with the monitored consumption of power if the high-speed quality events detected are above the predetermined threshold, and disregarding the detected high-speed quality events if the detected high-speed quality events are below the predetermined threshold; a multiplexor for combining the stored detected high-speed quality events in time synchronization with the monitored consumption of power to display the monitored consumption of power and the detected high-speed quality events in a single waveform representation; and the memory for storing the predetermined threshold, the monitored consumption of power, the detected high-speed quality events, and the single waveform representation, to be displayed for the user.
The method of operation for the revenue grade power meter capable of detecting high-speed power quality events of the preferred embodiment comprises monitoring and recording consumption of power by a user for metering purposes at a first scanning rate; detecting and recording high-speed quality events of the power consumed by the user at a second scanning rate, the second scanning rate being faster than the first scanning rate; and combining both recorded results to display the power monitoring result and the detected high-speed quality events in a single waveform representation.